An arrangement is known in which an actuator applies a reaction force to an accelerator pedal depending on the depressed amount of the accelerator pedal, i.e., the amount at which the accelerator pedal is depressed. See, for example, International Publication No. 2009/136512 (hereinafter referred to as “WO2009/136512A1”) and Japanese Laid-Open Patent Publication No. 2007-026218 (hereinafter referred to as “JP2007-026218A”).
According to WO2009/136512A1, the actuator has a reaction force applying characteristic, which is set depending on a target speed in order to assist the driver in operating the accelerator pedal (see, for example, Abstract and FIGS. 3A through 3C).
According to JP2007-026218A, an accelerator pedal (3) and a servomotor (19) are connected to each other by a pedal lever (5) and an arm member (15). The servomotor has a drive shaft (19b) with a gear (19a) connected to a distal end of the drive shaft, and the gear (19a) is held in mesh with teeth (15b) of the pedal lever. The structural members apply a reaction force from the servomotor to the accelerator pedal (see Abstract and FIG. 1).
As described above, according to JP2007-026218A, a reaction force is transmitted through a speed reduction mechanism including a gear (19a) and teeth (15b). However, nothing is disclosed in the description of JP2007-026218A concerning details (gear ratio, etc.) of the speed reduction mechanism.
FIGS. 1, 2, and 4 of JP2007-026218A show a gear and teeth. Judging from the figures, even if the gear of the motor were rotated to a maximum extent, only a portion of the gear will come into contact with or mesh with the teeth, thus leaving another portion of the gear which never meshes with the teeth. Therefore, a large force is continuously applied to only the portion of the gear that is held in mesh with the teeth, thereby causing the gear to have a region that is intensively worn, as well as a region that is not worn at all. As a result, even when the gear of the motor is rotated maximally, a liability exists for the gear to become less durable than if the gear was constructed such that it meshes with the teeth over the full circumference thereof.
The fact that only a portion of the gear is held in mesh with the teeth upon rotation of the gear of the motor to a maximum extent implies that the drive shaft of the motor is angularly moved through an angle that is smaller than 360°. Therefore, not only the gear, but also various other parts of the motor are subject to localized forces, thus making the motor less durable than if averaged forces were applied to parts of the motor. If the motor comprises a brush motor, then the commutator of the brush motor contacts the brushes within a limited range, such that only particular regions of the brush motor wear easily. In such a case, steps tend to develop between regions that are intensively worn and regions that are not intensively worn, resulting in a reduction in durability of the motor. Furthermore, noise and load differences occur due to different amounts of wear (different resistances to rotation of the motor), which could possibly make the user feel strange concerning the manner in which the reaction force pedal device operates.